Potassium channels play an important role in regulating cell membrane excitability. When the potassium channels open, changes in the electrical potential across the cell membrane occur and result in a more polarized state. A number of diseases or conditions can be treated with therapeutic agents that open potassium channels. See K. Lawson, Pharmacol. Ther., v. 70, pp. 39-63 (1996); D. R. Gehlert et al., Prog. Neuro-Psychopharmacol & Biol. Psychiat., v. 18, pp. 1093-1102 (1994); M. Gopalakrishnan et al., Drug Development Research, v. 28, pp. 95-127 (1993); J. E. Freedman et al., The Neuroscientist, v. 2, pp. 145-152 (1996). Such diseases or conditions include asthma, epilepsy, hypertension, impotence, migraine, pain, urinary incontinence, stroke, Raynaud's Syndrome, eating disorders, functional bowel disorders, and neurodegeneration.
Potassium channel openers also act as smooth muscle relaxants. Because urinary incontinence can result from the spontaneous, uncontrolled contractions of the smooth muscle of the bladder, the ability of potassium channel openers to hyperpolarize bladder cells and relax bladder smooth muscle provides a method to ameliorate or prevent urinary incontinence.
WO 9408966 and EP 0539154 A1 disclose a group of acridinedione and quinolone compounds that are claimed useful in the treatment of urinary incontinence. These compounds belong to the larger general chemical class of dihydropyridines. The compounds of the present invention are chemically distinct from those of WO94/08966 and EP 0539154 A1 since they have at least one sulfonyl group attached to the 3-position of the dihydropyridine ring.
Dihydropyridines of differing chemical structure may possess a variety of biological activities. For example, U.S. Pat. No. 4,879,384 discloses a group of thiacycloalkeno[3,2-b]pyridines that belong to the dihydropyridine class and are calcium channel antagonists. The compounds of the present invention are chemically distinct from those of U.S. Pat. No. 4,879,384 since they do not have a carboxylic acid derivative attached to the 3-position of the dihydropyridine ring.
Thus, the compounds of the present invention are chemically distinct from the prior art, hyperpolarize cell membranes, open potassium channels, relax smooth muscle cells, inhibit bladder contractions and are useful for treating diseases that can be ameliorated by opening potassium channels.